A-Level Biology AQA 7402

Nutrients are recycled within natural ecosystems, exemplified by the nitrogen cycle and the phosphorus cycle.

Microorganisms play a vital role in recycling chemical elements such as phosphorus and nitrogen.

• The role of saprobionts in decomposition.
• The role of mycorrhizae in facilitating the uptake of water and inorganic ions by plants.
• The role of bacteria in the nitrogen cycle in sufficient detail to illustrate the processes of saprobiotic nutrition, ammonification, nitrification, nitrogen fixation and denitrification.

(The names of individual species of bacteria are not required).

The use of natural and artificial fertilisers to replace the nitrates and phosphates lost by harvesting plants and removing livestock.

The environmental issues arising from the use of fertilisers including leaching and eutrophication.